#algo #ruby

max_traveled_distance.rb

# You are driving a car.
# You start moving with a velocity of V1 meters per second.
# Every second you can change your velocity with D meters per second.
# After T seconds, you want to be driving with a velocity of V2.
# What is the maximum distance you can travel during those T seconds?

# 5
# 6
# 4
# 2
# Expected output: 26
# Explanation: 5 + 7 + 8 + 6

# 14
# 14
# 11
# 0
# Expected output: 154
# Explanation: You cannot change your velocity, therefore 14 * 11 = 154

def solution(cur_speed, target_speed, delta, seconds)
	if seconds == 1
		if cur_speed == target_speed
			return cur_speed
		else
			return nil
		end
	end

	solutions = []
	delta.times do |i|
		res1 = solution(cur_speed+i+1, target_speed, delta, seconds-1)
		if res1
			solutions << res1+cur_speed
		end
		res2 = solution(cur_speed-i-1, target_speed, delta, seconds-1)
		if res2
			solutions << res2+cur_speed
		end
	end

	if delta == 0
		return cur_speed * seconds
	end
	
	unless solutions.empty?
		return solutions.max
	end
end

v1 = gets.chomp.to_i
v2 = gets.chomp.to_i
t = gets.chomp.to_i
d = gets.chomp.to_i

p solution(v1, v2, d, t)